Gas-powered motor vehicles are today operated primarily using so-called liquefied gases and natural gases. Liquefied gases, such as auto gas (LPG=liquefied petroleum gas), which arise as a byproduct of hydrogenating processes in petroleum refining, are usually based on petroleum, and essentially consist of propane and butane. Natural gas (CNG=compressed natural gas) is mainly methane, and is obtained from extraction from natural gas sources.
In motor vehicles operated with natural gas, storing a higher quantity of fuel requires that the gas fuel in the gas tank be compressed under a high pressure, for example measuring 200-300 bar. For combustion engine operation, the compressed gas fuel must then again be relieved to a suitable low gas pressure, which most often lies below 10 bar, for example measuring approx. 8 bar. The gas fuel is relieved in a pressure reducer hooked up to the gas fuel line, from which the relieved gas stream is routed to respective fuel injection valves (“fuel injectors”) for injection into the intake tract of the combustion engine.
While filling up the motor vehicle at the gas station, practice has shown that the gas fuel compressed to a high gas pressure is often contaminated with the lubricating oil of the compressor used for filling up the tank. This is caused by the increasingly shorter times between consecutive refueling stops owing to the continually growing number of gas-powered motor vehicles. As a result, the operating temperature in the high-pressure stages of the compressor can rise so severely that lubricating oil evaporates and gets into the gas tank of the motor vehicle in gaseous form or as an aerosol with the gas fuel.
If the gas fuel in the pressure reducer is relieved to a gas pressure of 8 bar, for example, the gas fuel cools as pressure is relieved, so that the entrained oil constituents condense and are present in the gas fuel in liquid form or as an aerosol. The flow dynamics cause the oil contained in the gas fuel to become distributed unevenly to the fuel injectors, which can give rise to varying flow characteristics in the fuel injection valves and problems in exhaust gas treatment. As a result, it may not be possible to observe exhaust gas provisions over the route traveled, and drivability problems may be encountered. In addition, there is a danger that vehicle components, such as catalytic converters, might be damaged. The fuel injectors have also been observed to bond or gum to the oil constituents contained in the gas fuel.
In order to avoid these problems, it is known for vehicles to incorporate an oil separator in the gas fuel line between the gas tank and fuel injectors. Such an oil separator is normally installed on the low pressure side of the pressure reducer, the advantage to which his that the oil separator need only be pressure resistant to low pressure, and that the oil condensed on the low pressure side of the pressure reducer is easier to separate in liquid form or as an aerosol.
Oil separators used to date are designed in such a way that the gas fuel passes through a fleece filter so as to separate out the oil constituents contained in the fuel. However, a fleece filter essentially only makes it possible to trap the oil constituents present in the form of an aerosol in the gas fuel. If the gas fuel contains a larger quantity of liquid oil, this normally leads to the rapid saturation of the fleece filter, and decreases the filter effectiveness. The gas flow allows the oil contained in the fleece filter to “power through” to the clean gas side, the disadvantageous consequence of which is that the gas fuel becomes contaminated again.
By contrast, at least one object of the present invention is to provide an oil separator with which oil constituents can be reliably and safely removed from the gas fuel. In addition, other objects, desirable features, and characteristics will become apparent from the subsequent summary and/or detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.